Calcinosis of chronic renal failure is a rare cause of soft tissue calcifications in haemodialysis patients with chronic renal failure. This condition is characterised by the deposition of calcium phosphate crystals in the periarticular soft tissues, resulting in large calcified masses.

Terminology

Calcinosis of chronic renal failure is a secondary form of calcinosis and should not be confused with primary tumoural calcinosis, which is a rare familial condition characterised by painless, periarticular masses in young patients with normal kidney function.

Epidemiology

In dialysis patients, the frequency of calcinosis is estimated to be 0.5-7% ¹. The average time of appearance of the mass after the start of dialysis is variable, from a few months to several years ².

Pathology

Although the pathophysiology has not been fully elucidated, the increase of the phosphocalcic product seems to play a determining role, more than severe hyperparathyroidism. Indeed, several cases of calcinosis have already been reported without associated hyperparathyroidism or after parathyroidectomy ¹.

Location

Calcinosis is most often located in the vicinity of large joints (e.g. hips, knees, shoulders, elbows), and sometimes on the extremities ². The overlying skin is usually normal.

Radiographic features

On imaging, calcinosis of chronic renal failure is indistinguishable from primary tumoural calcinosis. The diagnosis is therefore based solely on clinical and biological findings.

Plain radiograph

Calcinosis has a typical appearance on plain radiographs with amorphous, cystic and multilobulated ("cloud-like") calcification located in a periarticular distribution ⁴.

CT

CT better delineates the calcific mass and may show cystic appearance with multiple fluid-calcium levels caused by calcium layering (sedimentation sign) ⁴.

Destruction of the adjacent bone is rarely described and may be the result of erosion due to repeated microtrauma to the bone caused by the large size of the mass and its periarticular location ³.

MRI

MR imaging with T2-weighted sequences shows heterogeneous high-signal intensity, even though there is a significant amount of calcification. T1-weighted sequences usually show heterogeneous lesions with low signal intensity ⁴.

Differential diagnosis

General imaging differential considerations include:

• primary tumoural calcinosis.
• hyperparathyroidism: most frequently in chronic renal failure
• calcium pyrophosphate deposition disease (CPPD)
• myositis ossificans
• calcinosis circumscripta
• calcinosis universalis
• milk-alkali syndrome
• hypervitaminosis D
• calcific tendinitis
• synovial osteochondromatosis
• synovial sarcoma
• osteosarcoma
• calcific myonecrosis
• tophaceous gout